iphone 6 dead after iOS 9.3.1 update

It's not even clear that you have a genuine iPhone if you got it from some fly-by-night website.

For a start restore iOS using iTunes on your computer and Recovery mode: If you can't update or restore your iPhone, iPad, or iPod touch - Apple Support

If that fails, try again using DFU Mode:

• Install the latest version of iTunes on your computer if it isn't there already ( (you must have Windows 7 or later or OS X 10.8.5 or later)
• Reboot your computer
• Disable any antivirus and firewalls
• Launch iTunes
• Connect the device cable to a USB port on the computer (not to a USB hub), but DO NOT CONNECT TO THE DEVICE YET
• Press and hold the HOME and SLEEP buttons at the same time for 8 seconds, until the screen turns black, then release the SLEEP button but continue holding the HOME button. If an Apple logo appears while holding both buttons you held for too long; start over.
• While still holding the HOME button connect the other end of the cable to the device
• You should see a message in iTunes saying a phone in Recovery mode has been detected (it may take up to a minute for the message to appear). When you see that message release the HOME button and the device should restore. When asked DO NOT restore a backup; set up as a new phone.

I had something similar with my iPhone 6. 1 year and a month old and during the update my phone shut down and kept on showing that I had to connect it to iTunes. tried everything, update and restore and nothing worked. went to Apple store and they tried the same way to restore it with their Mac and still not turning on and still showing to connect to iTunes. Anyways all of that to finally say there is nothing we can do your phone is dead. Obviously my warranty finished 45 day before that happened.....